TY - JOUR
T1 - Folate-deficiency-induced homocysteinaemia in rats
T2 - Disruption of S-adenosylmethionine's co-ordinate regulation of homocysteine metabolism
AU - Miller, J. W.
AU - Nadeau, M. R.
AU - Smith, J.
AU - Smith, D.
AU - Selhub, J.
PY - 1994
Y1 - 1994
N2 - In a recent hypothesis, we proposed that homocysteinaemia arises from an interruption in S-adenosylmethionine's (AdoMet) coordinate regulation of homocysteine metabolism. The present study was undertaken to test a prediction of this hypothesis, that homocysteinaemia due to folate deficiency results from impaired homocysteine remethylation due to the deficiency and impaired synthesis of AdoMet, with the consequent inability of this metabolite to function as an activator of homocysteine catabolism through cystathionine synthesis. Rats were made folate-deficient by feeding them with a folate-free amino-acid-defined diet supplemented with succinylsulphathiazole. After 4 weeks, the deficient rats exhibited a 9.8-fold higher mean plasma homocysteine concentration and a 3.2-fold lower mean hepatic AdoMet concentration compared with folate-replete controls. Subsequent supplementation for 3 weeks of the folate-deficient rats with increasing levels of folate in the diet resulted in graded decreases in plasma homocysteine levels, accompanied by graded increases in hepatic AdoMet levels. Thus plasma homocysteine and hepatic AdoMet concentrations were inversely correlated as folate status was modified. In a second experiment, the elevation of plasma homocysteine in the deficient rats was found to be reversible within 3 days by intraperitoneal injections of ethionine. This effect of ethionine is thought to be exerted through S-adenosylethionine, which is formed in the liver of these rats. Like AdoMet, S-adenosylethionine is an activator of cystathionine β-synthase and will effectively promote the catabolism of homocysteine through cystathionine synthesis. In crude liver homogenates of the rats treated with ethionine, cystathionine β-synthase activity was 3-fold higher than that measured in homogenates from vehicle-treated controls.
AB - In a recent hypothesis, we proposed that homocysteinaemia arises from an interruption in S-adenosylmethionine's (AdoMet) coordinate regulation of homocysteine metabolism. The present study was undertaken to test a prediction of this hypothesis, that homocysteinaemia due to folate deficiency results from impaired homocysteine remethylation due to the deficiency and impaired synthesis of AdoMet, with the consequent inability of this metabolite to function as an activator of homocysteine catabolism through cystathionine synthesis. Rats were made folate-deficient by feeding them with a folate-free amino-acid-defined diet supplemented with succinylsulphathiazole. After 4 weeks, the deficient rats exhibited a 9.8-fold higher mean plasma homocysteine concentration and a 3.2-fold lower mean hepatic AdoMet concentration compared with folate-replete controls. Subsequent supplementation for 3 weeks of the folate-deficient rats with increasing levels of folate in the diet resulted in graded decreases in plasma homocysteine levels, accompanied by graded increases in hepatic AdoMet levels. Thus plasma homocysteine and hepatic AdoMet concentrations were inversely correlated as folate status was modified. In a second experiment, the elevation of plasma homocysteine in the deficient rats was found to be reversible within 3 days by intraperitoneal injections of ethionine. This effect of ethionine is thought to be exerted through S-adenosylethionine, which is formed in the liver of these rats. Like AdoMet, S-adenosylethionine is an activator of cystathionine β-synthase and will effectively promote the catabolism of homocysteine through cystathionine synthesis. In crude liver homogenates of the rats treated with ethionine, cystathionine β-synthase activity was 3-fold higher than that measured in homogenates from vehicle-treated controls.
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M3 - Article
C2 - 8135750
AN - SCOPUS:0028347021
VL - 298
SP - 415
EP - 419
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
IS - 2
ER -